On Fri, 25 Jan 2008, Andrea Arcangeli wrote: > On a technical merit this still partially makes me sick and I think > it's the last issue to debate. > > @@ -971,6 +974,9 @@ int try_to_unmap(struct page *page, int > else > ret = try_to_unmap_file(page, migration); > > + if (unlikely(PageExternalRmap(page))) > + mmu_rmap_notifier(invalidate_page, page); > + > if (!page_mapped(page)) > ret = SWAP_SUCCESS; > return ret; > > I find the above hard to accept, because the moment you work with > physical pages and not "mm+address" I think you couldn't possibly care > if page_mapped is true or false, and I think the above notifier should > be called _outside_ try_to_unmap. Infact I'd call > mmu_rmap_notifier(invalidate_page, page); only if page_unmapped is > false and the linux pte is gone already (practically just before the > page_count == 2 check and after try_to_unmap).
try_to_unmap is called from multiple places. The placement here also covers f.e. page migration. We also need to do this in the page_mkclean case because the permissions on an external pte are restricted there. So we need a refault to update the pte. > I also think it's still worth to debate the rmap based on virtual or > physical index. By supporting both secondary-rmap designs at the same > time you seem to agree current KVM lightweight rmap implementation is > a superior design at least for KVM. But by insisting on your rmap > based on physical for your usage, you're implicitly telling us that is > a superior design for you. But we know very little of why you can't We actually need both version. We have hardware that has a driver without rmap that does not sleep. On the other hand XPmem has rmap capability and needs to sleep for its notifications. > Nevertheless I'm very glad we already fully converged on the > set_page_dirty, invalidate-page after ptep_clear_flush/young, > etc... and furthermore that you only made very minor modification to > my code to add a pair of hooks for the page-based rmap notifiers on > top of my patch. So from a functionality POV this is 100% workable > already from KVM side! Well we still have to review this stuff more and I have a vague feeling that not all the multiple hooks that came about because I took the mmu_notifier(invalidate_page, ...) out of the macro need to be kept because some of them are already covered by the range operations. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
